Date: Tue, 10 May 2005 00:16:56 -0400 From: Suleiman Souhlal <ssouhlal@FreeBSD.org> To: Daniel Eischen <deischen@FreeBSD.org> Cc: freebsd-stable <freebsd-stable@FreeBSD.org> Subject: Re: Performance issue Message-ID: <361776BC-F969-4F88-8656-E75A5D967186@FreeBSD.org> In-Reply-To: <Pine.GSO.4.43.0505091907060.27904-100000@sea.ntplx.net> References: <Pine.GSO.4.43.0505091907060.27904-100000@sea.ntplx.net>
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Hello, On May 9, 2005, at 7:21 PM, Daniel Eischen wrote: > I don't think that patch is correct. You need the signal mask > in the kernel to match in case of an exec() after a fork() > for instance. If the application fork()'s, then changes the > signal mask in the child (which is now single threaded), then > the child exec()s, the mask is wrong. > > If the process wasn't linked to libpthread, then the longjmp() > and setjmp() would still be calling the syscall, so it isn't > the syscall itself that is making things slower. You'll notice > that there are two calls to __sys_sigprocmask() in the section > of code you have patched. You could eliminate the second call > if you do some of what the remainder of the function does instead > of returning early (the locks aren't needed and pending signals > don't need to be run down). Processes linked with libc_r NEVER call the syscall, once they have started (after rtld-elf): zZzZ:~/py% LD_LIBMAP="libpthread.so.1=libc_r.so.5" ktrace -t c python heapsort.py 10000 > /dev/null && kdump -T | grep sigprocmask 2991 python 1115698354.240301 CALL sigprocmask (0x1,0x2810a820,0xbfbfea60) 2991 python 1115698354.240304 RET sigprocmask 0 2991 python 1115698354.240307 CALL sigprocmask(0x3,0x2810a830,0) 2991 python 1115698354.240308 RET sigprocmask 0 zZzZ:~/py% compare with libpthread: zZzZ:~/py% ktrace -t c python heapsort.py 10000 > /dev/null && kdump - T | grep -c sigprocmask 92114 zZzZ:~/py% Is this a bug in libc_r? -- Suleiman Souhlal | ssouhlal@vt.edu The FreeBSD Project | ssouhlal@FreeBSD.org
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